Objective The role of the skin
Roles of anti-bodies
Phagocytes
B-lymphocytes
T-lymphocytes
Role of vaccines
Bacterial and viral infections
The Immune System The immune system is the body’s natural defense against
disease-causing agents such as bacteria, viruses and parasites. The immune system is made up of a complex and vital network
of cells and organs that protect the body from infection. It plays an important role in identifying and eliminating
abnormal cells.
The Human Immune System is divided into two broad groups : Acquired Immune System
Always working to protect the body and does not require any special preparation to stop infection.
Innate Immune SystemNeeds to be 'primed' before it can work to its full
effectiveness though, and is only really effective after it has seen a possible infective agent before.
The Immune System
Innate Immunity Acquired Immunity
B-Cell Immunity
T-Cell Immunity
Resistance of skin
Destruction of organisms by the acids in the stomach
Chemical compounds in the blood
Cells called ‘Macrophages’ that ingest foreign objects
Consist of B-cells
Produce Anti-Bodies
Involved with Primary and Secondary response
Consists of T-Cells
T-Cells are: T helper cells T killer cells
Structure and organs of the Immune System The structures of the immune system, detailing the
parts of the body that play a role in immunity. These include:– The lymphatics– Lymph nodes
Lymphatic Organs and Structures
– Thymus– Spleen
Lymph– A fluid containing:
Water Sugars Salts Waste White Blood
Cells Protein
Lymph Vessels– Carry lymph within
the lymphatic system
– Lymph capillaries are the smallest of the lymph vessels
The Immune system
Adenoids Tonsils
Thymus
Spleen
Payer’s Patches
Bone marrow
Lymph Nodes
Lymphatic Vessels
Appendix
7
Capillaries Capillaries have thin walls which allow fluid in body
tissues to flow between the capillaries and tissues.
Fluid in the spaces between tissues is called interstitial fluid
Once the interstitial fluid flows into the lymph capillaries it is called lymph
Lymphatic trunk
Right lymphatic duct or thoracic duct
Right subclavian vein (neck)
Lymphatic vessel
Lymphatic capillary
Interstitial fluid
Blood stream
Structure and organs of the Immune System
Lymphatic VesselsPulmonary capillary network
Blood flow
Systemic capillary network
Lymphatic capillaries
Lymph node
Lymphatic vesselsLymph flow
Lymph node
Lymph flow
Lymphatic capillaries
Structure and organs of the Immune System
9
Lymph Nodes Specialized organs that produce lymphocytes. Filter harmful substances from the tissues. Contain macrophages that devour foreign substances. Lymphocytes produce specialized proteins called antibodies
that fight disease. Antigens also fight disease by stimulating an immune
response in other cells.
Structure and organs of the Immune System
Lymph Travels in only one direction. Empties into the right thoracic duct and the lymphatic duct. Lipids are transported from the small intestines to the blood
stream by the lymph vessels.
Location of major groups of lymph nodes:- Tonsils -Mediastinum-Groin-Neck-Adenoids -Armpit
Spleen Largest lymphatic organ located in upper left portion of the
abdominal cavity. Filters foreign material from the blood. Destroys old red blood cells Activates lymphocytes
Structure and organs of the Immune System
Thymus Gland Soft gland with two lobes Larger during infancy and childhood Contains important cells called thymocytes T cells (T lymphocytes provide immunity) Thymosin aids with T cell movement
Major PlayersThe major players in the immune system include:– Macrophage– T cells (helper, cytotoxic, memory)– B cells (plasma, memory)– Antibodies
White Blood Cells – LymphocytesThe lymphocytes are of 2 types
• T lymphocytes • B lymphocytes
Higher rank officials of the immune system and have a sophisticated mode of action.
Their importance is highlighted by the fact, that an absence of lymphocytes, which occurs in AIDS, leaves the body unprotected from infections and finally leads to early death.
B- lymphocytes The B lymphocytes are present in lymph nodes. Upon finding the relevant antigens get activated and
transform themselves to plasma cells. Plasma cells secrete large quantities of antibodies
corresponding to the antigen found by the B lymphocytes. These antibodies circulate in blood and attach to all
infecting organisms and cells present in the body having the concerned antigen.
T- lymphocytes This helps them recognize all the tissues of one’s own body. Their response to an overwhelming infection, is in the form of
multiplication of the particular cell family concerned with destruction of the particular foreign antigen.
They not only destroy the antibody coated cells but also stimulate activation and formation of plasma cells by B lymphocytes.
The T lymphocytes are highly specialized and trained cells, which intelligently tackle infections by recognizing and multiplication of a specific lineage of cells, which perform higher immune functions.
Antibodies
Antibodies are assembled out of protein chains.
There are many different chains that the immune system assembles in different ways to make different antibodies.
Antibodies as Receptors
Antibodies can attach to B cells, and serve to recognize foreign antigens.
Antigens as Effectors
• Free antibodies can bind to antigens, which “tags” the antigen for the immune system to attack and destroy.
Role of antibodies
Antibodies released into the blood stream will bind to the antigens that they are specific for.
Antibodies may disable some microbes, or cause them to stick together (agglutinate).
They “tag” microbes so that the microbes are quickly recognized by various white blood cells.
Role of Skin
Dead skin cells are constantly sloughed off, making it hard for invading bacteria to colonize.
Sweat and oils contain anti-microbial chemicals, including some antibiotics.
Role of mucus and cilia
Mucus contains lysozymes, enzymes that destroy bacterial cell walls.
The normal flow of mucus washes bacteria and viruses off of mucus membranes.
Cilia in the respiratory tract move mucus out of the lungs to keep bacteria and viruses out.
Nasal mucosa
Role of phagocytes
Phagocytes are several types of white blood cells (including macrophages and neutrophils) that seek and destroy invaders. Some also destroy damaged body cells.
Phagocytes are attracted by an inflammatory response of damaged cells.
The not-so-common cold
A “cold” is an infection of the mucus membranes of the respiratory tract by a rhinovirus.
Over 100 rhinoviruses have been identified, which is one reason why we don’t become immune to “the cold.”
Virus vs. Bacteria
Colds and influenza are caused by viruses.
Viruses are which is a non-living particle that contains genetic material, and hijacks your cells to reproduce.
Viruses cannot be “killed” with antibiotics.
Rhinovirus
Influenza virus
Virus vs. Bacteria
Bacteria are living organisms that have a metabolism, have DNA, and can reproduce on their own.
Bacteria can be killed with antibiotics because these substances target key processes in bacteria, such as production of the bacterial cell wall.
E. coli
Streptococcus
Helping the Immune System
Medical science has created to systems for augmenting the human immune system:– Antibiotics– Vaccines
How antibiotics work
Antibiotics help destroy bacteria (but not viruses).
Antibiotics work in one of several ways:– Slowing bacteria reproduction.– Interfering with bacterial cell wall formation.
How vaccines workModern vaccines are created from killed
bacteria or viruses, or fragments of proteins from these microbes.
The proteins are recognized as antigens by our immune systems. This causes a mild immune response. Memory T-cells and B-cells remain ready to fight off the illness if it is encountered again.
AIDS
AIDS (Acquired Immune Deficiency Syndrome) is caused by an infection by the HIV (Human Immunodeficiency Virus), which attacks and destroys T-helper cells. Because it attacks the immune system directly, finding a vaccine has been difficult.
Some drugs can slow down HIV reproduction, but no cure exists yet. Prevention is still the best “cure.”
AIDSThe HIV virus fools helper T-cells into thinking its proteins are “self,” and so is able to infect the cells that trigger specific immunity.
The virus forces T-cells to make more viruses, killing the T-cells when the new viruses burst out.
AIDS Prevention
HIV is a fragile virus that cannot live outside the human body for more than a few minutes.
Preventing HIV spread comes down to preventing exposure to body fluids of an infected person.
The End
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